Common Rust
 

My 1983 280zx has a rust problem where the battery box is, this is a common problem and I was wondering what would be an easy fix to eliminate the weak spot in my car.

Z rust is common, period. :)

The fix would be to chop out the rust, and replace. Do you have auto body repair experience? If so, go to it. If not, it's not something "easy". You need to understand what to remove, how to remove it, and how to install it. Drills, air chisel, MIG welder, clamps, metal brake, hammer & dolly, weld through primer, primer & paint supplies, etc, are all things you'll need. PurePontiacKid has been restoring a 280zx body and just posted pics the other day on FB of his repaired / modified battery tray. I'll see if I can find it.

Rust -_- its the only thing that holds my car back. Yesterday i found some right under the seal of the hatchback right above the hatch lock it was hidden real well. i found it trying to remove the key cylinder to make another key. I was going to take collision repair classes to learn to remove rust but the program is no longer available for free so insisted im going for engine analysis. But i recommend taking those classes i thing they will help alot